1. Field of the Invention
The invention relates to a digital circuit arrangement for influencing the frequency response of a digital audio signal as a function of frequency and/or amplitude.
2. Description of the Related Art
Such circuit arrangements are particularly necessary in noise suppression systems which are to suppress the noise arising after a sound carrier has been recorded and subsequently reproduced. Such known systems are, for example, the DBX, the HIGHCOM system and the various Dolby systems. In the latter noise suppression systems, a predefined effect on the audio signals, is set as a function of the frequency and the amplitude of a signal. Such systems are usually referred to as sliding-band systems.
An encoder is provided for these noise suppression systems which increases the upper frequency range of the audio signal at the recording end, for example, as a function of the frequency and/or amplitude of the signal, and a decoder which reduces the same frequency range in a mirror-inverted manner.
For most noise suppression systems of the type described above, it holds that only circuit arrangements operating in the analog mode are known for them. The cause of this is that the circuit arrangements are generally used only for analog audio signals. Of late, however, digitally operating devices for reproducing audio signals have increasingly been marketed, which are also to be suitable for the reproduction of, for example, audio signals.